Published March 1977
This report is a supplement to Process Economics Program Report No. 36, "Low Density Polyethylene," April 1968. In that report three processes were evaluated. All of the processes have reactors that operate at high pressures (1000-3000 atm) and use free radicals as initiators for the polymerization reaction. One of the two principal processes uses a tubular reactor in which a portion of the large heat of polymerization is removed in cooling jackets. The other principal process uses an autoclave reactor in which heat removal capability does not exist or is at most very limited. The third process, using gamma radiation to generate the required free radicals, was in an early stage of development in 1968 and now appears to have been shelved.
In this supplement the autoclave and tubular reactors have been redesigned on the basis of new information. Single-line reactor capacities have increased markedly in recent years. For both types of process, single-line capacities of 100,000 metric tons/yr (220 million lb/yr) have been used as the design basis, whereas in 1968 for 200 million lb/yr, two lines were used in the autoclave process and four lines were used in the tubular process. In other respects the polymerization flow schemes are similar to the previous schemes. The finishing and storage sections have been completely redesigned.
One of the most important design parameters is the per pass conversion of ethylene. The effects on the economics of varying the ethylene conversion have been examined both from the standpoint of design basis and from the standpoint of operation of an installed plant. The plant designs are based on producing ethylene homopolymers. The economics of producing ethylene copolymers have been evaluated on the basis of using an autoclave type, low density polyethylene plant in blocked-out operation.
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